javascript Quirky JS（IEEE-754） - 安全地将小数舍入到一个位置

Posted 2021-05-03

// Case Usage: You want to add decimal values but need to do a comparison
// 0.2 + 0.1 != 0.3 >>> 0.30000000000000004
// 0.2 + 0.4 != 0.6 >>> 0.6000000000000001
// 0.2 + 0.7 != 0.7 >>> 0.8999999999999999

function onePlace(a, b) {
  
  return Math.round( (a + b) * 10 ) / 10;
  
}

roundToOnePlace(0.1, 0.2);
// >>> 0.3

// this value can then be used in a comparison check in expected manner
// this is better than toFixed() as it returns a number and not a string